BRASSINOSTEROIDS: Essential Regulators of Plant Growth and Development

Abstract

Brassinosteroids (BRs) are growth-promoting natural products found at low levels in pollen, seeds, and young vegetative tissues throughout the plant kingdom. Detailed studies of BR biosynthesis and metabolism, coupled with the recent identification of BR-insensitive and BR-deficient mutants, has greatly expanded our view of steroids as signals controlling plant growth and development. This review examines the microchemical and molecular genetic analyses that have provided convincing evidence for an essential role of BRs in diverse developmental programs, including cell expansion, vascular differentiation, etiolation, and reproductive development. Recent advances relevant to the molecular mechanisms of BR-regulated gene expression and BR signal transduction are also discussed.

Seed dormancy and germination

“…Brassinosteroids (BRs), are naturally occurring plant steroid hormones found in a wide variety of plant species (Clouse and Sasse, 1998) are also involved in the control of germination in Arabidopsis. The BR signal leads to reduced sensitive to ABA and thereby stimulates germination, although the normal germination of BR deficient and BR signalling mutants indicates that there is no absolute BR requirement for germination (Steber and McCourt, 2001).…”

“…This cold effect is mediated by a light stable bHLH transcription factor SPATULA (SPT), which suppresses the expression of these genes (Penfield et al, 2005). In addition cold may increase the sensitivity of seeds to GAs because it also has an effect in GA deficient mutants .The fact that often stratification is more effective than GA treatment (Alonso-Blanco et al, 2003) suggests that also other factors, promoting germination, are affected by stratification.Brassinosteroids (BRs), are naturally occurring plant steroid hormones found in a wide variety of plant species (Clouse and Sasse, 1998) are also involved in the control of germination in Arabidopsis. The BR signal leads to reduced sensitive to ABA and thereby stimulates germination, although the normal germination of BR deficient and BR signalling mutants indicates that there is no absolute BR requirement for germination (Steber and McCourt, 2001).…”

The brassinosteroid signal transduction pathway

“…Physiological studies have demonstrated that BR can induce diverse cellular responses such as stem elongation, pollen tube growth, leaf bending and epinasty, root inhibition, induction of ethylene biosynthesis and fruit ripening, and xylem differentiation [3][4][5][6]. The identification of Arabidopsis BR biosynthetic mutants established that BR is a new class of phytohormone with an essential role in plant growth and development [7][8][9].…”

Yaprak Senesensi: Fizyolojik ve Moleküler Düzenlenmesine Bakış

“…İlk olarak, 2,4-epi-brassinolide (eBR) in dışsal uygulamasının fasulye yapraklarında [48], salatalık kotiledonlarında [49] ve domates meyvalarında [50] senesensi teşvik ettiği gösterilmiştir. İkinci olarak, BR biyosentezi (örn; det2) ya da BR sinyal yolu (örn; bri1) eksik olan Arabidopsis mutantları gecikmiş yaprak senesensi fenotipi göstermektedirler [51]. bri1 fenotipini baskılayan bir mutasyon belirlenmiştir.…”